Knuckle structure for railway vehicle coupler

ABSTRACT

A coupler including a knuckle having a convex gathering surface formed by an arc of fixed radius of which the arc approximates a portion of a spiral. The arcuate surface is generated so that in the open position of the knuckle the resultant force of the force normal to the face and the friction force at the point of contact along the length of the gathering surface is incapable of overcoming the resisting force at the pivot pin until the tip of the knuckle nose has passed a mating closed coupler.

States Patent [191 Altherr [lll 3,872,978

[ Mar. 25, 1975 KNUCKLE STRUCTURE FOR RAILWAY VEHICLE COUPLER PrimaryExaminer-M. Henson Wood, Jr. Assistant Examiner-Gene A. Church [57]ABSTRACT A coupler including a knuckle having a convex gathering surfaceformed by an arc of fixed radius of which the arc approximates a portionof a spiral. The arcuate surface is generated so that in the openposition of the knuckle the resultant force of the force normal to theface and the friction force at the point of contact along the length ofthe gathering surface is incapable of overcoming the resisting force atthe pivot pin until the tip of the knuckle nose has passed a matingclosed coupler.

2 Claims, 2 Drawing Figures KNUCKLE STRUCTURE IFOR RAILWAY VEHICLECOUPLER BACKGROUND AND SUMMARY OF THE INVENTION Coupling of railway carsis generally accomplished with the coupler knuckle on one car closed andthe mating coupler knuckle on the other car open. Although under somecircumstances both of the couplers may be open. At the samt time, thetrack conditions or the couplers may be located suchthat thelongitudinal axis of the mating couplers are not aligned. In order toachieve coupling it is necessary that the couplers be swung relative toeach other during the initial contact so that the coupler axes arebrought into axial alignment.

The extent to which the couplers may be axially misaligned and movedinto coupling engagement is desig nated as the lateral gathering range.Heretofore, the standard gathering range required by the A.A.R.(American Association of Railroads) is about l fliinch. This limitedgathering range has not eliminated passed couplers during couplingthereby causing coupler or car damage.

The alignment of the couplers into axial alignment occurs as a result ofthe force exerted at the knuckle faces during the initial and subsequentcontact. This force must be sufficient to apply a moment with overcomesthe sum of the coupler carrier friction moment and butt resisting momentof the shank of the coupler .thereby to cause the couplers to swingabout the butt end. However, the force at the engaging knuckle facesmust be controlled to permit sliding of the knuckle faces as thecouplers swing into alignment without causing the knuckle of the opencoupler to close prematurely before it passes beyond the tip of thenose. Should the open knuckle close prematurely, the closed knuckle isprevented from entering into coupled engagement with the mating closedcoupler.

By the present invention it is proposed to provide a coupler having animproved knuckle contour which achieves a greater gathering range thanpossible heretofore without premature closing of the open knuckle.

This is accomplished by forming the gathering face on the knuckle in theform ofa convex surface ofan arc of fixed radius which approximates aportion ofa spiral. Preferably, the gathering face is contoured toapproximate an arc of an equi-angular spiral so that the resultant forceof the force of friction and the force normal at any point of contactalong the entire length of the convex gathering surface is incapable ofturning the knuckle from an open to a closed position until the tip ofits nose has passed the tip of a mating coupler.

Further features will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a top plan view of a couplerincorporating the improved knuckle structure of the present inventionshown in coupling relationship with a coupler of conventional structureand shows the vector relationship of the forces for turning the couplersinto longitudinal axial alignment.

FIG. 2 is a fragmentary view ofa coupler knuckle incorporating theimproved gathering face contour of the present invention and showing inphantom the improved gathering surface and graphically illustrating themanner in which the theoretical spiral curve and actual curve isobtained and the resolution of the vector forces associated with curvedsurface on the knuckle.

DESCRIPTION OF THE PREFERRED EMBODIMENT fixed to one end of a shank l4.The'shank I4 is provided with a key slot 16 which receives the key (notshown) associated with the draft gear (not shown) mounted in the centersill (not shown) of the railway car on which the coupler is mounted. Thecoupler I 10 is horizontally swingable about its cylindrical butt 17 inthe usual manner.

For convenience the corresponding components of the coupler 11 areidentified with the same reference character, but with an a suffix. Thecoupler 11 includes a coupler head or housing 13a, a knuckle 12a, ashank 14a, a draft key pocket 16a and a butt 17a. The coupler 10 andcoupler 11 are shown with the longitudinal axes 18 and 18a offset withrespect to each other..

As is well known the knuckle .12 isattached to the knuckle side 19 ofthe housing 13 by means of a pivot pin 21 whereby the knuckle 12 isswingable between an open position and a closed position. Similarly, the

knuckle 12a is swingable about a pivot pin 21a.

As mentioned above, the couplers l0 and 11 in FIG.

. l are shown offset or laterally displaced to illustrate the gatheringrange. When railway vehicles are approaching for coupling one or both ofthe knuckles may be open. Usually, however, coupling occurs with oneknuckle open and the mating coupler closed. To achieve coupling, thecouplers must be swung about therespective butt ends into longitudinalalignment. At the same time, the open knuckle must remain in the openposition while sliding along .the closed knuckle until thetips 25 and25a ofthe noses of the two knuckles pass. After the tips 25 and 25a passthe open knuckle may be closed into coupling engagement with the matingclosed coupler in the usual manner.

When the knuckles are both in the open position, at least one of theknuckles must remain open so that the tips of the noses similarly passeach other. It should be readily apparent that premature closing of theopen knuckle when the other knuckle is closed results in failure tocouple.

In accordance with the present invention the coupler knuckle 12 isprovided with a convex gathering surface 22. The convex gatheringsurface 22 is located to lie in the path of movement of a buffing noseof a mating coupler.

The upper end of the convex surface 22 is located, as illustrated inFIG. 1, so that when contacted by a mating coupler the moment Rd,wherein R is the resultant force of the friction force fN and the forceN normal to the point of contact, exceeds the sum of the carrierfriction moment Wb and the buff resisting moment Pa. Under theseconditions swinging movement of the coupler about its butt end 17 isinitiated. The surface 22 is curved so that the resultant force R as theknuckles slide produces a moment about the butt 17 which continues toswingthe couplers into axial alignment.

The convex surface 22 is also curved so that the resultant force R atany point of contact along the curved surface 22 lies along a line whichdoes not create an cecentric moment arm relative to the turning axiscausing the open knuckle 12 to close prematurely before it passes thetip a of the closed knuckle. After the nose tips 25 and 25a pass, theknuckle 12 may turn to a closed position to couple with the closedknuckle 12a, in the usual manner.

The convex or curved gathering face 22 is generated along a curve sothat the resultant force R at any point of contact along the lengththereoflies on a line passing approximately the same distance from thepivot center c so as not to overcome the friction forces at the pivotpin 21. The frictional resistance about the pivot pin 21 may berepresented as a vector by the friction circle FC shown. The frictioncircle radius r may be calculated by the formula r =fr wherein r is theradius of frictional contact about the pivot pin 21 andfis thecoefficient of friction. From the foregoing it should be apparent thatturning is prevented as long as g r. This may be achieved by maintainingthe resultant force along a line approximately tangent to the frictioncircle FC. Preferably, the eccentricity is maintained-substantiallyequal to r. I

The curved surface achieving the desired relationship between and r isobtained by shaping the gathering face 22 as a spiral curve I as shownin phantom of FIG. 2 and having an equation p Ire wherein p is theradial distance from the center of pivot to any point on the gatheringsurface 22, ii! is the angle in radians from a reference line B-B, e isthe value 2.71828 ofthe base of the natural system of logarithms; k isthe magnitude ofp when ll! 0; m is the coefficientthat establishes therate of increase of the spiral radius; (m is also equal to the tangentof the angle A between the radial direction of p and the direction ofthe normal force N at any point on the curve 22.)

The value ofk and m necessary to prevent premature closure of theknuckle is dependent on the friction angle (1) at the points of contactofthe coupling knuckle and the coefficient of frictionfabout the pivotpin 21. The parameters of a satisfactory curve between the points T andS as shown in FIG. 2 may thus be expressed by the relationship p sin( k)r.

The curved surface 22 as shown is constructed so that one end T used asthe reference for determining ill ing of nose tips 25 and 25a with amating coupler. The curve I shown in phantom lines was generated from avalue of coefficient of frictionfwhich has been generally accepted asbeing present at the knuckle faces upon contact. It is to be noted thatthe resultant force R at any point along the curve 22, when the aboverelationships are maintained, lies along lines which are approximatelytangent to the friction circle FC.

The curve I is constructed using the standard construction axis A-A of astandard knuckle and may be approximated by an arc which has a fixedradius Z to define the gathering surface 22. The center Y of the curvedsurface 22 having a fixed radius Z is located on the vicinity of the AAconstruction axis above the center C as illustrated. Preferably thecenter Y of the fixed radius Z is angularly displaced clockwise of axisA-A, as viewed in FIG. 2, thereby to provide a curvature which achievesapproximately the same force characteristics as the spiral curve I.

It should be understood that the arrangement described above constitutesthe preferred embodiment and that many adaptations and modifications maybe made without departing from the spirit of the invention. j

I claim:

1. A railway vehicle coupler comprising a coupler housing, a knuckle,knuckle pivot means mounting said knuckle on said housing for movementabout a pivot axis between an open position and a closed position. saidknuckle having a nose tip, a convex gathering surfaceextending from apoint closely adjacent to said nose tip', said gathering surface beingcurved such-that the resultant force of the force normal to the surfaceand the friction force at any point of contact along the length of thegathering surface lies along a line which passes approximately a sameselected distance from the pivot axis so as to be incapable ofovercoming the frictional resistance at said pivot means and thereby prevent premature closing, said curved gathering surface including the arcof a spiral having the equation: p ke wherein p is the radial distancefrom the pivot axis to any point on the gathering surface, ll] is theangle in radians from a reference point, e is the value of the logarithmto the base e. k is the magnitude of p when ll! O, m is equal to atangent k which is the angle between the radial direction of p and theline normal to the tangent of the curve, and said parameters of saidcurve are determined by the relationship p( )t) g r wherein d) is thefriction angle or are tangent of the coefficient of friction at thepoint of contact with a mating coupler, and r is the radius of afriction circle corresponding to the friction forces resisting turningof the knuckle about the pivot axis.

2. The invention as defined in claim 1 wherein said gathering surface isan are having a fixed radius and lying substantially on said spiralcurve.

* =l =l l

1. A railway vehicle coupler comprising a coupler housing, a knuckle,knuckle pivot means mounting said knuckle on said housing for movementabout a pivot axis between an open position and a closed position, saidknuckle having a nose tip, a convex gathering surface extending from apoint closely adjacent to said nose tip, said gathering surface beingcurved such that the resultant force of the force normal to the surfaceand the friction force at any point of contact along the length of thegathering surface lies along a line which passes approximately a sameselected distance from the pivot axis so as to be incapable ofovercoming the frictional resistance at said pivot means and therebyprevent premature closing, said curved gathering surface including thearc of a spiral having the equation: Rho kem wherein Rho is the radialdistance from the pivot axis to any point on the gathering surface, psiis the angle in radians from a reference point, e is the value of thelogarithm to the base e. k is the magnitude of Rho when psi 0, m isequal to a tangent lambda which is the angle between the radialdirection of Rho and the line normal to the tangent of the curve, andsaid parameters of said curve are determined by the relationship Rho (phi - lambda ) < OR = r1 wherein phi is the friction angle or arctangent of the coefficient of friction at the point of contact with amating coupler, and r1 is the radius of a friction circle correspondingto the friction forces resisting turning of the knuckle about the pivotaxis.
 2. The invention as defined in claim 1 wherein said gatheringsurface is an arc having a fixed radius and lying substantially on saidspiral curve.